Building board or the like



y 1966 J. PAGE ETAL BUILDING BOARD OR THE LIKE 2 Sheets-Sheet 1 Filed March 11, 1963 PENDLETON NEQMAIQ 52150;: ALWMLLKAMi GTQRNEXS y 1966 J- PAGE ETAL BUILDING BOARD OR THE LIKE 2 Sheets-Sheet 2 Filed March 11, 1963 PENDLETON NEUMRN SE4 BOLD F-WlLL\RMS QTY C RNEY 5 United States Patent 3,260,027 BUILDING BOARD OR THE LIKE John Page, Glenview, and Rupert J. Straub, Lisle, Ill., assignors to United States Gypsum Company, Chicago, Ill., a corporation of Illinois Filed Mar. 11, 1963, Ser. No. 264,084 2 Claims. (Cl. 52-602) This invention relates to a novel building board or the like constructed of gypsum. More specifically, it relates to a unique gypsum-containing board having spaced ribs on one side, which board lends i-tself to a great variety of uses including the formation of non-load-bearing studless partitions or the like and yet meets the demanding production, storage, shipping, installation, performance, appearance and cost requirements which have heretofore frustrated past efforts to achieve such a structure.

THE PROBLEM AND DEFICIENCIES OF PRIOR ART STRUCTURES Those skilled in the art have long recognized that one of the ultimates in the construction of interior partitions from the standpoint of minimum cost would be an allgypsum building board from which self-supporting or studless panels or the like could be constructed. The fact that an all-gypsum installation is or approaches the ultimate" is apparent from its many well-recognized desirable characteristics, combined with its abundant availability and low basic cost relative to alternative materials of construction.

Some prior-art efforts have met one .or more of the requirements for such a structure but have otherwise failed to meet all of the demanding requirements to a sufficient degree as to render the board feasible, practical and attractive from the standpoints of performance, appearance and installed cost. For example, acceptable board must lend itself to efiicient and continuous production on high-speed machinery such as is employed in connection with the production of conventional gypsum wallboard, e.g., as disclosed in Utzman US. Patent 1,330,413. Some prior-art boards, e.g., as shown in Sanborn US. Patent 1,679,947, did not lend themselves to high-speed production, necessitated excessive capital investment for highly-specialized production machinery and/or created still-unsolvable production problems, particularly in the area of gypsum drying.

Moreover, once a building board is manufactured, it must lend itself to compact stacking, handling and shipment without excessive damage under normal conditions and without storage or freight-cost disabilities. Some prior-art boards, while otherwise satisfactory, could not be compactly stacked with edges flush or handled and shipped without excessive damage losses or without undue storage and freight costs. This problem is aggragated where, as in the aforementioned Sanborn patent and in Finebrock et al. US. Patent 1,955,877, th ribs or projections are at the board edges and must be sufficiently elongated to extend the full panel void thickness.

Furthermore, the board itself must be large in size for rapidity of installation and yet must be strong enough and light enough to be readily manipulatable by a single workman. In conventional home construction, 4-foot by 8-foot gypsum boards are typical and, except for boards of extra thickness, do not exceed substantially about 100 pounds in weight and usually weigh less. Some proposed boards or panels of the prior art, however, failed to meet such standard and had insuflicient strength or were so heavy as to be unmanageable by the average workman.

Still further, the board must lend itself to on-site assembly into partitions and must be readily installable by tradesmen of average skills. Some prior-art boards, while otherwise satisfactory, must be factory-assembled into partitions or require too high a degree of skill arid/or effort by the average tradesman at the job site. For ex-' ample, in Bartholomew US. Patent 2,399,978, the tradesman must install at the job site costly spacers comprising a plurality of laminated layers of wallboard material.

In addition, the resulting construction must otherwise meet or exceed requisite structural and appearance standards already common to alternatives; e.g., conventional drywall construction. Here, again, some prior-art allgypsum panels were doomed to failure.

Because prior-art efforts have thus repeatedly failed to achieve an all-gypsum board meeting accepted appearance and structural standards at lower cost, the impression has grown in the trade that it could not be done. building board of the present invention, however, now establishes that it can and has been done.

It is therefore an object of the present invention to pro-' vide a gypsum building board or the like which permits all-gypsum, interior partition construction meeting accepted appearance and structural standards at lower cost. It is a further object of the present invention to provide such a building board and yet avoid the difiiculties, pitfalls and shortcomings encountered by the prior-art efforts along the same line. These and other objects of the present invention will become apparent as the detailed description of the present building board proceeds.

THE INVENTION The objects of the present invention have been achieved by a full recognition and appreciation of all of the problems associated therewith and the conception of a building board successfully coping with same. In brief, the novel board of the present invention comprises a gypsum-containing rectangular sheet which is substantially flat on the face side and has a plurality of spaced, longitudinallyextending, gypsum-containing ribs integral therewith protruding from the rear side thereof parallel to the longi tudinal edges. For structural integrity, the gypsum sheet must not be less than about A inch in thickness as measured between the ribs. The height of the ribs, in turn, should not be less than about the thickness of said sheet.

It is also important, particularly from the standpoint of controlled gypsum drying, that the average transverse thickness of the ribs be not less than about the thickness of said sheet and not more than about 3 /2 times the thickness of said sheet. In addition, the total of the transverse thicknesses of all ribs as measured at midheight should be between about 5 to 25 percent of the width of the building board itself. The spacing of the ribs preferably conforms to a modular pattern or design and permits nesting of the ribs of adjacent boards during storage and shipment, as hereinafter described in connection with the embodiments of the accompanying drawings.

The building 'board of the present invention also has a paper covering adhered to the face side and to the rear side. The term paper is intended to include any functional equivalent including natural or synthetic fabrics, porous films, and the like. The paper covering must have a tensile strength in all directions not less than about 15 pounds per lineal inch. The paper covering on the rear side may advantageously be single ply, perforated at the outermost surfaces of the ribs or otherwise strengthened, e.g., by sizing or impregnating with a strengthimparting binder material, for reasons pointed out here inafter.

To avoid undue cracking, it is essential that the ribs, particularly those adjacent the longitudinal edges of the board, have strengthening means adjacent the juncture of the ribs with the rear side. Such strengthening means may comprise, for example, non-stress-concentrating flared side portions of the ribs at the juncture, conveniently in the form of enlarged fillets, e.g., fillets having to /2 The gypsum inch radius. In another embodiment the strengthening means may comprise slurry-penetrable reinforcing webs adjacent the juncture, which webs optionally may connect the paper adhered to the rear side adjacent the respective ribs. Conveniently in such optional embodiment, the paper adhered to the rear side comprises a single fiat sheet with discontinuous apertures coextensive with the bases of the ribs, the ribs themselves being covered with separate paper strips adhered to the rear-side paper.

In still another particular and advantageous embodiment the ribs on the rear side have outermost surfaces parallel to the face side and have side portions substantially flared adjacent said outermost surfaces, whereby the area of the outermost surfaces exceeds the minimum cross-sectional area of the ribs, by, for example, at least about 10 percent, preferably '25 percent, but not substantially exceeding about 100 percent. In still another embodiment, the sheet is tapered adjacent the longitudinal margin or edges of the face side.

As should be apparent from the above description, a building unit may be readily formed from the gypsum board above described by adhering two of the boards together at the respective ribs of each (or to an intermediate flat gypsum board). This is typically accomplished in practice by erecting one board at the desired partition site by means of runners or the like; installing utilities, e.g., electrical outlets or the like, between rib locations; and then cementing the ribs of an opposed board to the ribs of the first-erected board, thereby completing the panel except for usual finishing and decoration.

THE DRAWINGS The building board of the present invention and its advantages will be better understood from the following detailed description, including the accompanying drawings wherein:

FIGURE 1 is a perspective view of one embodiment of the building board of the present invention with the flat or face side hidden and the rib side shown for clarity;

FIGURE 2 is a perspective view showing how a partition or the like may be formed by adhering together two boards of the type illustrated in FIGURE 1 at the respective outermost surfaces of the ribs of each;

FIGURE 3 is another perspective view showing how a partition or the like may be formed by adhering ribs together even though edges or margins of the respective boards do not coincide;

FIGURE 4 is an enlarged end view of portions of two building boards of the present invention which are nested together for compact storage or shipment, the ribs of each board being flared adjacent both the rib bases and the outermost surfaces and the edges of the board being tapered as in preferred embodiments;

FIGURE 5 is a similar enlarged end view of another embodiment wherein the outermost portions of the ribs are not flared;

FIGURE 6 is an enlarged perspective view of a portion of a panel made from still another embodiment of the building boards of the present invention, wherein ends of each board are broken away to show the strengthening means adjacent the bases of the ribs, which strengthening means comprise slurry-penetrable reinforcing webs; and

FIGURE 7 is a similar, enlarged perspective view of still other embodiments, the upper board showing the strengthening means to be part of a fiat sheet of paper adhered to the rear side of the board, the lower board showing the strengthening means to be an apertured web of paper adhered to the underside of the paper on the rear side.

DETAILED DESCRIPTION Referring to FIGURES 1, 2 and 3 together, building boards 10 comprise flat sheets of gypsum 11 (e.g., prepared from a cementitious slurry of calcium sulfate hemihydrate, water, starch, foam, fibers, set-accelerating reagents, etc.) having a plurality of spaced ribs 12 integral therewith and protruding from one side thereof. While the ribs appear to have square or rectangular cross-sections in FIGURES 1, 2 and 3, such is for convenience of illustration, the actual rib configurations more closely approximating those shown in FIGURES 4, 5, 6 and 7.

A typical board is 4 feet in width and from 8 to 14 feet in length with the ribs parallel to the edges or margins of the long side. As will also be discussed hereinafter in connection with the preferred modular spacing of the ribs, there are typically (but not necessarily) 6 to 8 ribs within the 4-foot width and the ribs are so spaced that ribs of opposed boards register and may be cemented together so as to produce panels such as are illustrated in FIGURES 2 and 3.

The modular spacing of the ribs is also patterned so that the boards may be nested together as shown in FIG- URES 4 and 5 to minimize storage and shipping space. For such purposes the rib spacing is also designed so that the edges or margins of the longitudinal sides are flush, i.e., in the same plane perpendicular to the faces. In contrast to staggered edges, the flush arrangement occupies less space and is less subject to damage during storage, handling or shipment.

As shown in FIGURES 1, 2, 3 and 5, the ribs may have substantially fiat sides towards the outermost surfaces. In a preferred embodiment, however, the ribs are substantially flared adjacent the outermost surfaces as indicated in FIGURES 4, 6 and 7. The flare is such as to provide an uppermost surface having an area at least 10 percent, preferably 25 percent, greater than the minimum transverse area at any point intermediate the outermost surface and the juncture of the rib with the rear surface. This configuration is corrective of one of the weaknesses experienced with prior art designs, which weaknesses are now discussed.

In this connection, it is to be noted that, contrary to a popular misconception, a ribbed, gypsum building board by itself is not necessarily stronger than ordinary fiat wallboard of the same sheet thickness. In fact, ribbed gypsum structures of the prior art have proved to be weaker. The present invention is in part an outgrowth of recognizing this fact and pinpointing the primary areas of weakness in prior-art ribbed gypsum structures and providing solutions thereto which are reconcilable and consistent with the many other requirements for a successful ribbed gypsum building board, as already indicated.

It should be understood that the primary strength of the ordinary flat sheet of gypsum board is derived from the ability of the paper adhered to the faces thereof to absorb the tensile forces to which the sheets may be subjected by flexure. The gypsum itself, While relatively strong under compression, has substantially less strength in tension. Accordingly, the tensile forces to which the flat face of the ribbed structure of the present invention is subjected are handled by providing cover paper having a tensile strength in all directions no less than about 15 pounds per lineal inch, preferably no less than about 25 pounds per lineal inch. Such paper is designated by the numeral 14 in FIGURES 4 through 7.

The paper 15 adhered to the rear or rib side of the boards in FIGURES 4 and 5, however, is not in a single plane and cannot absorb at rib locations the tensile forces to which the rib side may be subjected by lateral convex flexure. Thus, unless some corrective measures are taken, even slight convex flexure of the rib side may result in cracking of the board, invariably at the junctures of the ribs with the rear side, particularly in the case of the ribs adjacent the longitudinal edges of the board. This problem is coped with by providing strengthening means adjacent such junctures, which strengthening means may take a number of forms.

For example, as shown in FIGURES 4 and 5, fillets 16 (or equivalent stress-distributing flared portions) of very substantial radii, e.g., at least /s-inch radius, preferably at least A-inch, optimally /i-inch or more, are provided at the junctures. As one skilled in the art will recognize, the curvature of the fillets need not be constant so long as stress-concentrating abrupt changes in direction are avoided.

In another embodiment, as shown in FIGURE 6, the strengthening means comprises a reinforcing web 17 imbedded in the gypsum adjacent the junctures of at least the edge-adjacent ribs, preferably all the ribs. Such reinforcing web may take the form of an open-lace-work of strands of a suitable material, e.g., natural or synthetic fibrous materials, such as various plastics, e.g., polyethylene, polypropylene, or the like; glass; rayon; Dacron; or equivalents thereof. The web may also comprise an apertured sheet material or fabric, e.g., paper, the various aforementioned natural and synthetic materials, and equivalents thereof.

In another embodiment the strengthening web might merely comprise individual spaced strands or strips of such materials transverse to the ribs. Such uni-directional reinforcement is feasible because it is only in a lateral direction that the paper covering on the rib side does not provide substantial strengthening all across the board.

Where such strengthening webs are not adhered to the inside of the paper cover of the rear side, the shape, texture or nature of its surface thereof must be such as would hinder slippage through the set gypsum in which it is imbedded. Otherwise, the web would tend to slip and not absorb the tensile forces to which the structure might be subjected.

Whatever the strengthening means, it must be penetrable by a fluid slurry of calcined gypsum so as to provide a path for entry of same into the rib configuration during manufacture of the board. Such paths also assure partial continuity of the gypsum and minimize possible cleavage or slippage planes in the structure.

Other embodiments of the strengthening means are shown in FIGURE 7. For example, in the building board forming the upper portion of the panel of FIGURE 7 the strengthening means comprises slurry-penetrable, apertured web 18. In practice, it may be formed by employing a continuous flat sheet of paper for the rear side and providing a series of holes therein coextensive with the bases of the ribs. The paper cover of the rib itself is formed by a rib-covering paper strip 19 adhered both to the rib 12 itself and to the paper 18 adjacent the rib.

Another embodiment, similar to that of FIGURE 6, is shown in the building board forming the lower part of the panel of FIGURE 7. As in the embodiments of FIG- URES 4 through 6, the paper which covers the rear side including the ribs is formed from one continuous sheet with appropriate folds for the rib configurations. The strengthening means is provided by means of apertured webs 20, the side margins of which are adhered to the underside of paper 15.

It should be apparent that the apertured webs coextensive with the rib bases as shown in the embodiments of FIGURES 6 and 7 would be in tension when the rear-side of the board is convexly flexed laterally. The ability of the Webs to absorb the tensile forces at the rib locations supplements the tensile strength of the gypsum.

The apertures in the strengthening webs .of FIGURE 7 are for the same purpose as the openings in the reinforcing webs of FIGURE 6, i.e., to provide a path for flow of gypsum slurry during manufacture and to provide continuity to the gypsum structure without slippage or cleavage planes. The size of the openings is not critical so long as a gypsum slurry can rapidly flow therethrough. In practice, we prefer circular apertures of A-inch minimum diameter. Because of the strength-imparting function of the web and the need to avoid tearing thereof during manufacture of the board, the minimum cross-section of the web is-normally not reduced to less than percent of the total. Thus, for example, in the case of a web having circular apertures of one-inch diameter, the

inter-aperture web should be at least A-inch. The minimum-size inter-aperture web is, of course, a function of the inherent strength of the Web material, higher strength paper, for example, permitting smaller webs.

While various independent strengthening means are disclosed herein, it should be understood that each may be used alone'or in combination with any of the others. For example, in FIGURE 6, fillets or flared portions 16 adjacent the juncture of the ribs and rear side are employed to supplement strengthening webs 17. In contrast, in FIGURE 7 the flared portions are substantially eliminated and the primary reinforcement is derived from webs 18 and 20.

Another primary area of potential weakness in ribbed gypsum boards exists at the outermost surfaces of the ribs. These surfaces form the interface when the boards are adhered to each other to form a panel by paper-to-paper adhesives, for example, conventional starch, starch-modified and dextrin-based adhesives, preferably adhesives having substantial water resistance, particularly those which may impart strength to the paper and do not require heat, pressure or undue drying periods for strong joints, such as conventional joint cement; protein-type adhesives, e.g., animal glues, bone glues, hide glues, etc.; resin emulsion adhesives, optionally mixed with clay, e.g., polyvinyl acetate-based resinous emulsions, advantageously a polyvinyl acetate-poly-vinyl alcohol emulsion with clay filler; and functional equivalents thereof. It has been found, in general, that the cross-sectional area required for structural soundness at intermediate portions of the ribs is less than that required at such interface.

Accordingly, in a preferred embodiment, as aforementioned, the ribs are flared adjacent the outermost surfaces so as to provide a larger area for adherence. Other solu tions to the problem may be employed in place of or supplementary to flared portions. Such other solutions might include sizing of the paper, at least at the interface so as to strengthen same; the use of single-ply paper, e.g., Fourdrinier produced paper, instead of delaminationprone, multi-ply, cylinder-stock paper; the aperturing of the paper at the outermost surfaces so that gypsum-adhesive-gypsum adherence may be obtained, as well as contact of the adhesive with the various plies of paper; and the impregnation of the paper with, or incorporating therein during manufacture, a strength-imparting binding material, e.g., impregnation with a low-solids solution (prefer ably 3-7% solids) of a resin, the solution having high paper penetrability, such as solutions of esters of the natural resins, shellac, the natural gum adhesives, polyvinyl acetate, and functional equivalents thereof. In a particular embodiment, the strength-imparting binding material may also serve as the adhesive for adhering the ribs of two opposed building boards together to form a panel. For example, the outermost surfaces of the ribs may be coated with sufficient adhesive, e.g., a polyvinyl acetate-based adhesive, so that a portion of it will penetrate at least part way into the cover paper to bind same while the remainder of it will serve to adhere the respective ribs of opposed boards together. Other expedients for providing additional strength at the interface will be, in the light of the present disclosure, apparent to those skilled in the art.

Another important factor in assuring interface strength at all rib positions is uniformity of rib height, particularly as measured from the face side of the board. If rib height is not uniform, undersized ribs may require undue thicknesses of adhesive to bridge the gap to the corresponding ribs of an opposed board, with obvious problems attendant therewith. If contact or proper spacing for adhesion must be forced by flexing the board, undesired and unsightly depressions occur on the face side coextensive with the undersized ribs. Accordingly, the ribs of our building board have outermost surfaces parallel to the face side and of uniform distance from the face side, e.g., within about 0.030 of an inch. In short, the outermost surfaces of the ribs should be in substantially the same plane parallel to the plane of the face side.

As previously indicated, structural and weight considerations dictate that the total of the transverse thickness of all ribs as measured at midheight should be between about to 25 percent of the width of the building board.

Thus, in the case of a board having the conventional width of 48 inches, the total thickness of all ribs as measured at the half-way p-oint of rib height should roughly be between about 2 /2 inches and 12 inches. The measurement is made at the half-way point or midheight on the assumption that such location normally approximates the point of narrowest cross-section. If such is not so in any particular case, it should be understood that the narrowest cross-section is intended by such limitation.

Of critical importance is the relationship of rib thickness to the thickness of the board itself. A crucial problem in the high-speed production of gypsum articles is proper setting and drying of the calcined gypsuim slurry from which it is formed. The problem of drying is aggravated, as in the present invention, in the case of irregular cross-sections having variable thicknesses. If the board is under-dried at any portion, warping, distortion or other undesired dimensional or configurational changes result during subsequent storage or shipment. If the gypsum is over-dried so as to burn or calcine same, loss of strength of the bond of the paper to the gypsum and loss of structural integrity may result.

To cope with this problem, it has now been determined that if the thickness of each rib is no less than the minimum thickness of the sheet of gypsum intermediate the ribs and not more than about 3 /2 times such thickness, proper drying is possible on high-speed production machinery of the type presently available. This relationship is based on the assumption that rib height is at least equal to the rib thickness. There is no necessary upper limitation on rib height other than recognized practical considerations, including the increased proneness of high ribs to breakage upon handling, problems of compact stacking, and the like. In general, rib height varies from about 1 to 5 times the thickness of the sheet of gypsum intermediate the ribs.

The above criteria provide some of the bases for deciding upon the number and size of ribs to be used in any particular board. The spacing of the ribs is dictated largely by the obvious necessity for support across the width of the board and the present trend towards the design of building structures in a modular pattern.

One aspect of modular design is the predictability of repetition of construction features, e.g., the 16-inch spacing of conventional studdi ng; the sizing of construction components in standard increments, e.g., 4-inch increments or multiples thereof, or the like. One modula-r pattern which is gaining acceptance today is the 4-inch module, although other modular patterns are also being considered. For practical reasons, most modular patterns are based on whole-inch intervals integrally divisible by an integer greater than one.

As applied to the building board of the present invention, modular spacing of the ribs must also take into consideration the requirement for compact stacking during storage and shipment, e.g., by the nesting of. the ribs of opposed boards, and, in addition, the requirement that the edges of the board be flush, rather than staggered, when stacked. The building board of the present invention fully lends itself to all of such requirements as specific examples of successful embodiments. hereinafter illustrate.

SPECIFIC EXAMPLES Example 1 To conform with the popular 4-inch modular pattern, building boards of the present invention were prepared having the rib spacing such as shown in FIGURES 1-3,

8 the rib configurations themselves being uniform and conforming generally to that illustrated in FIGURE 4. Each of the building boards was 4 feet in width and 8 feet in length, the 7 ribs thereon extending lengthwise.

The thickness of the sheet between ribs was about inch. The height of the ribs was approximately /8 inch, as measured from the rear side of the board or 1% inches as measured from .the face side. All of the outermost surfaces of the ribs thus lay in a common plane parallel to the plane of the face side of the board. As one skilled in the art will recognize, a rib height of 4; inch results in a panel with l.%-II1C11 voids, which is ample to accommodate a nominal 2-by-2-inch wood support or the fiat side of a nominal 2-by-4-inch stud. Closer fits or largersize voids may be obtained by decreasing or increasing rib height respectively. For example, by decreasing rib height to -7 inch, a 1%-inch void results, which snugly accommodates wood structural members having 2-inch nominal size.

The transverse thickness of the ribs at the midheight point was about 78 inch, and the outermost surface had a transverse width of approximately 1% inches because of the flared portion adjacent thereto. The bases of the ribs were strengthened by means of enlarged fillets having a minimum radius of curvature of about inch, the maximum exceeding /2 inch.

The face and rear sides of the boards had multiaply paper adhered thereto, and adherence of the paper to the gypsum being obtained by contact therewith while setting and drying. The paper adhered to each side had a minimum tensile strength substantially in excess of 15 pounds per lineal inch. The longitudinal edges of the boards were tapered as indicated in FIGURE 4, the taper commencing at about 2% inches to 2% inches in from the edge and resulting in a reduction in edge thickness of about 0.035 to 0.040 inch. Tapering of the edges is designed to compensate for the thickness of joint tape and cement when the face sides of adjoining boards are conventionally finished.

As illustrated in FIGURE 1, the center line of the first rib on the right-hand side was spaced from the edge by about 1% inches. The second-through-sixth ribs were spaced at successive 8-inch reenter-line intervals from said first rib, and the 7th rib on the left-hand side of FIGURE 1 was spaced at a 4-inch center-line interval from the adjacent 6th rib. The center line of the last rib was therefore about 2% inches from the adjacent edge of the board.

It should be apparent from the above description that the board of FIGURE 1 as above dimensioned constitutes a 4-inch modular pattern and can be made to register with identical boards to form panels as illsutrated in FIGURES 2 and 3. It is also apparent that since the center iine of the rib adjacent one edge of the board is spaced about 1% inches from the edge and the center line of the rib adjacent the other edge is spaced 2% inches therefrom, it is possible, by proper placement of opposed boards to nest the respective ribs thereof with the edges flush, as indicated in FIGURE 4. In short, with the respective edges flush, the inner side extremity of the rib of the lower board of FIGURE 4 clears the outer side extremity of the rib of the upper board.

The ability to nest the boards is a highly attractive feature because of storage and shipping savings. For example, if the ribs of the board of the present example could not be nested, two such boards would occupy a space of 2 /2 inches. With ribs nested, however, two such boards would occupy only 1% inches, a substantial space saving.

The rib sizings and spacings required to achieve both modular pattern and the ability to nest ribs for any particular size board will be apparent from the above description to those skilled in the art. For example, for a board having a width equal to fou-r times an integral multiple of one inch, e.g., 32-inch or 48-inch boards, the ribs may v 9 be spaced, center line to center line at Whole-inch intremity of one of the edgewise ribs should be no more I V l trons adjacent lllC Olllliflllll than two inches from the edge.

For a board having a smdth equal to SlX times an integral multiple of one which also includes 48-inch boards, the ribs may be spaced at whole-inch intervals integrally divisible by slit and the inner side extremity of one of the edgewise ribs should be no more than three inches from the edge. For a board having a width equal to eight times .an integral multiple of one inch, which likewise includes 48-inch boards, the ribs may be spaced at whole-inch intervals integrally divisible by eight and the inner side extremity of one of the edgewise ribs should be no more than four inches from the edge.

While the board of the present example had the specific rib spacing and dimensions as set forth above, it should be kept in mind that such dimensions and spacing may be varied to achieve particular objectives. For example, if nominal 2-by-2-inch wood splines are to be used at the edges of panels constructed therefrom, rib thickness, height, configuration, spacing and/ or strengthening means may be readily worked out in the light of'the present disclosure to provide the desired end result, i.e., a space of at least 1% inches between the inner sides of the sheets of gypsum and ribs recessed from the edge by at least 7 inch.

Example 2 To conform to a 6-inch modular pattern, building boards of the present invention are prepared having 4- foot widths and 8-foot lengths with 8 ribs of substantially uniform cross-section on one side thereof extending lengthwise. The thickness of the gypsum board between ribs i /8 inch. The height of the ribs is inch as measured from the rear side of the board or 1 inches as measured from the face side. All of the outermost surfaces of the ribs lay substantially in a common plane parallel to the plane of the face side of the board.

Each of the 8 ribs has a transverse thickness of about /8 inch at midheight and a cross-sectional configuration similar to that of FIGURE 4. Because of the flared portions adjacent the outermost surfaces, the width of the outermost surfaces is approximately 1 /8 inches.

The center line of one of the ribs is spaced 2 inches from a lengthwise edge. Each of the other 7 ribs is spaced 4 at successive 6-inch center-line intervals therefrom. Thus, the center line of the other edgewise rib is 4 inches from the corresponding edge. The boards are otherwise. as set forth in Exam-ple l.

The 6-inch modular pattern of this example permits the ribs of opposed boards to be nested for storage or shipment with the edges flush. When two such boards are adhered to each other at the outermost surfaces of the respective ribs, a partition or panel of enhanced suitability for interior construction results. This panel has a void space therein of 1% inches, which is sufficient to snugly accommodate a wood structural member having a nominal size of two inches.

Example 3 To conform to an 8-inch modular pattern, building boards of the present invention are prepared having 4- foot widths and 8-foot lengths with 6 ribs of substantially uniform cross-section on one side thereof extending lengthwise. The thickness of the gypsum board between ribs is /8 inch. The height of the ribs is Ms inch as measured from the rear side of the board or 1% inches as mesured from the face side. All of the outermost surfaces of the ribs lay substantially in a common plane parallel to the plane of the face side of the board.

Each of the 6 ribs has a transverse thickness of about /3 inch at midheight and a cross-sectional configuration similar to that of FIGURE 4. Because of the flared porlhc center line of one of the ribs in spaced 2 from a lengthw se edge. Each of the other rib" i at successrve ii-mch center-line intervals omen-J1 h bllaiuml the center line of the other edgcwisc rib is 5 2 from the corresponding ed e Th as set forth in Example 1. g c boards are othcrwlsc 'At inchca 0 STRUCTURAL TESTS Test A 20 Building boards substantially as described in Example 1 above were subjected to a series of tests to compare structural performance with conventional wallboard having the same gypsum composition and paper coverings. In these tests, which were designed to determine relative stiffness, the deflections of the ribbed board under various bending loads were compared with the deflections of conventional /2-inch gypsum wallboard under the same loads.

In each test seven increasingly-heavy loads were applied at the midpoint of a sample of each board. Each sample was 16 inches w-ide and 50 inches long and was suspended horizontally between supports spaced 48 inches on it d' l point of loaonr Midpoint Deflection (Inches) Applicants l Load, Lbs. Board wallboard Ribs Ribs Face Face Up Down Up Down It is apparent from these data that the building board of the present invention deflected less than half as much under the same load as conventlonal wallboard having the same gypsum content and cross-sectional area. It is therefore more than twice as stiff, a desired attribute.

Test B all samples was also perpendicular to the supports so as to take advantage of the relatively-higher strength of the paper in the fiber (or machine) direction. Deflection or sag meausrements were made at the one-quarter points at midspan after each sample had been exposed to the high-humidity conditions for a 24-hour period. The results were as follows:

24-Hour Sag (Inches) Applicants %-Inch Board Wallboard Ribs Ribs Face Face Up Down Up Down 1st Quarter Point; 100 088 .263 297 2nd Quarter Point. 110 105 262 302 3rd Quarter Point 106 072 259 315 Average .105 .088 .261 .305

These data establish that under high-humidity conditions applicants board was greatly superior to conventional /2-inch wallboard from the standpoint of resistance to sag.

Test C Another series of tests was carried out wherein the ability of panels constructed from building boards of the present invention to stand impact loads was compared with that of conventional wood stud-gypsum wallboard panels.

For such purposes Panel A was constructed by cementing together the respective ribs of two 4-foot by 8-foot building boards, said boards substantially as described in Example 1, resulting in an overall panel thickness of 2 inches. Panel B was constructed by cementing the ribs of one 4-foot by 8-foot building board substantially as described in Example 1 to a conventional 4-foot by 8- foot, As-inch-thick gypsum wallboard, resulting in an ov-erall panel thickness of 1% inches. The adhesive employed in constructing Panels A and B was a polyvinyl acetate-based resinous emulsion.

For comparison, Panel C was constructed by nailing two conventional 4-foot by 8-foot, /s-inch-thick gypsum wallboards to opposite sides of wood studs. The panel had four longitudinally-running, equally-spaced studs, two of which were at the respective longitudinal edges. The panel also had two laterally-running wood plates or studs at the respective lateral edges. The two longitudinally-running interior studs and the two laterally-running edge studs had 1%-inch by 2 /s-inch cross-sections (nominal 2-inch by 3-inch studs); and the two longitudinally-running edge studs had yi -inch by 2 /6-lI'1Ch cross-sections (nominal l-in-ch by 3-inch half studs).

The studs of Panel C were oriented so that the 2%- inch dimension was perpendicular to the gypsum wallboards forming the opposed face sheets, resulting in an overall panel thickness of 3% inches. Each of the face sheets was secured to the studs by fifty-four lMt-inch nails at intervals of approximately 8 inches. The laterally-running studs were secured :to the longitudinally-trunning studs by two IO-pen-ny nail-s at each stud intersection.

Each of the three p anels was supported horizontally as simple beams with a span length of 7 feet-6 inches and subjected to impact tests in accordance with the test procedure of ASTM E72-55 for Impact Load. In

these tests a 60-pound sand bag having a diameter of 10 inches was dropped to the geometric center of the top panel face from increasing heights starting at 1%. inches from the panel face. The energy and height of drop required to bring out initial cracking and rupture of the panel face was recorded, as follows:

These data establish that the ribbed building board of the present invention is capable of withstanding a much greater degree of impact before cracking or rupture than comparable WOOd stud-gypsum wall board panels.

In summary, an all-gypsum building board is herewith provided which meets the demanding production, storage, shipping, installation, performance, appearance, and cost requirements which have doomed prior art all-gypsum panels to failure. The board lends itself to efiicient production on high-speed machinery such as is presently employed in the industry. The board, which does not require that ribs be located at the edges or extend the full panel-void thickness, lends itself to compact edge-flush stacking, handling and shipment without excessive damage and without storage or freight c'ost disabilities.

The board may be made in large sizes for rapidity of installation and yet is is light enough and strong enough to be readily handled by a lone tradesman without breakage. The board may be (assembled into partitions rat the time of application, and the skills required for installation are well within those of an average tradesman. Appearance-wise, it is at least the full equivalent of conventional drywall construction and in some respects is superior thereto. For example, because between-rib adhesive replaces most of the nails used for conventional drywall, less surface marri-ng occurs and less finishing is required. In addition, post-installation problems such as nail p opping and the like are greatly reduced. In short, a superior installation at lower cost is provided by the building board of the present invention.

While the present building board is intended primarily for assembly at the job site into partitions, it will be recognized that it lends itself to factory assembly of complete panels. It will also be recognized that it lends itself to a variety of uses in addition to that already indicated.

SOME OTHER USES Alternative uses in the field of interior partitions and lathing systems include its use as hollow partitions comparable to what the industry knows as double solid partitions and also as a core unit for fire-rated partitions. The building board may also be employed as a self-furring la-th for masonry by cementing the rib side directly to masonry walls. A resilient partition system of reduced sound transmission may also be formed by cementing the ribs of opposed boards to an intermediate resilient material such as 'foam rubber rather than to each other. Voids in any such partition may be partially or completely filled .with thermal or sound insulating material or any other material desired, such as foam rubber or insulation board.

The board may also be used in ceiling systems as a lay-in ceiling unit. It might also be used as a sofiit board. In roof-deck systems it may be used as a dry roof deck unit or a form board for poured gypsum roof deck construction. As those skilled in the art will recognize, such specifically mentioned alternative uses by no means exhaust the many possibilities for the present building board.

While the building board of the present invention has been described with particular reference to certain specific examples, such specific c mmpfcs are l llltljliitlggL i niodifications fsi l xlrelzilgig mm from above q ri tion to those skilled in the art, Such other alternatives are considered Withing the spirit and scope of the present invention, and

coverage thereof is intended by this application.

Having described the invention, What is claimed is:

1. A selt-supporting panel construction comprising a pair of substantially-identical ribbed building boards adhered at outermost surfaces of opposed registering ribs, each of said ribbed building boards comprising a gypsumcontaining oblong-rectangular sheet substantially flat on the face side and having a plurality of spaced, longitudinally-extending gypsum-containing ribs integral therewith protruding from the rear side thereof and disposed asymmetrically about the longitudinal center line of said board, said sheet being not less than about A inch in thickness intermediate the ribs, each of said ribs being substantially parallel to and spaced from the longitudinal edges and being not less than about the thickness of said sheet in height with an average transverse thickness not less than about the thickness of said sheet and not more than about 3 /2 times the thickness of said sheet, the total of the transverse thicknesses of all ribs as measured at mid-height being between about 5 to 25 percent of the Width of the building board, each of said ribs also having outermost surfaces substantially in a .w /1111 [l /(J .tl/U/l [mil/1t may /)L Hat/01f W/l/l film/2] 01/1201: flush, said sheet being not less than about /i inch in thickness intermediate the ribs, each of said ribs being substantially parallel to and spaced from the longitudinal edges and not less than about the thickness of said sheet in height with an average transverse thickness not less than about the thickness of said sheet and not more than about 3 /2 times the thickness of said sheet, the total of the transverse thicknesses of all ribs as measured at midheight being between about 5 to 25 percent of the width of the building board, each of said ribs also having outermost surfaces substantially in a plane parallel to the face side and strengthening means adjacent the juncture of said ribs with said rear side, said face side and rear side with ribs each having a paper covering adhered thereto, the paper covering having a tensile strength in any direction no less than about 15 pounds per lineal inch.

References Cited by the Examiner UNITED STATES PATENTS 906,025 12/1908 Howe 52443 1,381,823 6/1921 Grifiin 52277 1,382,550 6/1921 Routt et a1. 52451 1,487,370 3/ 1924 Birdsey 52451 1,559,134 10/1925 Utzman 52376 1,853,310 4/1932 Land 52452 1,871,318 8/1932 Greenwood 52724 2,073,673 3/1937 Blake 52408 

2. BUILDING BOARD SUITABLE FOR FORMING SELF-SUPPORTING PARTITIONS, SAID BUILDING BOARD COMPRISING A GYPSUM-CONTAINING OBLONG-RECTANGULAR SHEET SUBSTANTIALLY FLAT ON THE FACE SIDE AND HAVING A PLURALITY OF SPACED, LONGITUDINALLYEXTENDING, GYPSUM-CONTAINING RIBS INTEGRAL THEREWITH PROTRUDING FROM THE REAR SIDE THEREOF AND DISPOSED ASYMMETRICALLY ABOUT THE LONGITUDINAL CENTER LINE OF SAID BOARD SO THAT TWO SUCH BOARDS MAY BE NESTED WITH BOARD EDGES FLUSH, SAID SHEET BEING NOT LESS THAN ABOUT 1/4 INCH IN THICKNESS INTERMEDIATE THE RIBS, EACH OF SAID RIBS BEING SUBSTANTIALLY PARALLEL TO AND SPACED FROM THE LONGITUDINAL EDGES AND NOT LESS THAN ABOUT THE THICKNESS OF SAID SHEET IN HEIGHT WITH AN AVERAGE TRANSVERSE THICKNESS NOT LESS THAN ABOUT THE THICKNESS OF SAID SHEET AND NOT MORE THAN ABOUT 3 1/2 TIMES THE THICKNESS OF SAID SHEET, THE TOTAL OF THE TRANSVERSE THICHNESSES OF ALL RIBS AS MEASURED AT MIDHEIGHT BEING BETWEEN ABOUT 5 TO 25 PERCENT OF THE WIDTH OF THE BUILDING BOARD, EACH OF SAID RIBS ALSO HAVING OUTERMOST SURFACES SUBSTANTIALLY IN A PLANE PARALLEL TO THE FACE SIDE AND STRENGHTENING MEANS ADJACENT THE JUNCTURE OF SAID RIBS WITH SAID REAR SIDE, SAID FACE SIDE AND REAR SIDE WITH RIBS EACH HAVING A PAPER ADHERED THERETO, THE PAPER COVERING HAVING A TENSILE STRENGTH IN ANY DIRECTION NO LESS THAN ABOUT 15 POUNDS PER LINEAL INCH. 